1. Field of Invention
The present invention relates to a stage device and an exposure apparatus, and more particularly, to a stage device having a plurality of stages, and an exposure apparatus having the stage device.
2. Description of Related Art
Various types of exposure apparatus are conventionally used in photolithographic processes for manufacturing semiconductor devices (ICs), liquid crystal display devices, and the like. In recent years, stepping projection exposure apparatus, such as a step-and-repeat reduction projection exposure apparatus (a so-called xe2x80x9cstepperxe2x80x9d) and a step-and-scan projection exposure apparatus (a so-called xe2x80x9cscanning stepperxe2x80x9d) have been mainly used.
Since this type of projection exposure apparatus is principally used to mass-produce semiconductor devices and the like, it has been inevitably necessary to increase the number of wafers to be exposed in a given period, that is, to enhance throughput.
Operation of the projection exposure apparatus is generally carried out in the following manner:
(a) First, a wafer is loaded onto a wafer table by a wafer loader in a wafer loading step.
(b) An alignment step is performed so as to find the positions of the shot areas on the wafer. The alignment step usually employs EGA (Enhanced Global Alignment). In this method, the positions of alignment marks (wafer marks) made in a plurality of sample shot areas selected beforehand from the shot areas of the wafer are sequentially measured, and layout data on all the shot areas is found by statistical calculations using the so-called least squares method or the like based on the results of measurement and the designed shot layout (see Japanese Unexamined Patent Application Publication No. 61-44429 and U.S. Pat. No. 4,780,617 corresponding thereto). This makes it possible to find the coordinate position of each shot area with high throughput and with relatively high precision.
(c) In the next exposure step, the shot areas on the wafer are sequentially positioned at an exposure position based on the coordinate positions thereof determined by EGA or the like and the previously measured base line distance, and an image of the pattern on the reticle is transferred onto the wafer via a projection optical system.
(d) In a wafer unloading step, the wafer on the wafer table, which has been exposed, is unloaded by using a wafer unloader. This step is performed simultaneously with the above-described wafer loading step (a). That is, the steps (a) and (d) form a wafer replacement step.
In the conventional projection exposure apparatus, broadly, three operations, wafer replacement, alignment, and exposure, are thus repeated on one wafer stage.
Accordingly, by concurrently performing at least parts of the above three operations, i.e., wafer replacement, alignment, and exposure, throughput can be made higher than that in a case in which the operations are sequentially performed. Exposure is not carried out during wafer replacement and alignment. In order to reduce the operating time, that is, to enhance throughput, for example, a stage for wafer replacement and alignment and a stage for exposure are concurrently and independently controlled.
An exposure apparatus having such two stages, which are independently movable, (hereinafter referred to as a xe2x80x9ctwin-stage type exposure apparatusxe2x80x9d) is disclosed in, for example, U.S. Pat. No. 5,715,064.
In the exposure apparatus disclosed in the above publication, alignment is effected on one of the stages concurrently with exposure of a wafer on the other stage. In this case, throughput is markedly enhanced, compared with the case in which alignment and exposure are sequentially effected.
When two wafer stages are simply placed, however, the footprint of the exposure apparatus is increased.
In order to effect high-precision exposure, the wafer table with the wafer thereon must be driven for Z-driving so as to control the focusing and leveling of the wafer during alignment as well as exposure. Since two wafer stages are placed side by side on a surface plate in the conventional twin-stage type exposure apparatus, however, reaction force produced due to the Z-tilting driving of the wafer table on one of the wafer stages, which is subjected to exposure, may vibrate the wafer table on the other wafer stage, and this may result in lower exposure accuracy.
The present invention has been made in view of the above circumstances, and a first object of the present invention is to provide a stage device which has a footprint equivalent to that of a single-stage type stage device and which allows two stages to be independently and freely moved.
A second object of the present invention is to provide an exposure apparatus which reduces the footprint thereof and enhances throughput and exposure accuracy.
According to a first aspect of the present invention, there is provided a stage device having a first stage and a second stage, including: a first driving device having a first moving member and a first stationary member so as to drive the first stage in a first direction; a second driving device having a second moving member and a second stationary member so as to drive the second stage in the first direction; a first guide bar provided with the first stationary member so as to movably support one side of the first stage; and a second guide bar provided with the second stationary member so as to movably support one side of the second stage, the second guide bar being placed at a predetermined distance from the first guide bar in a second direction orthogonal to the first direction.
In the above stage device, the first stage is driven along the first guide bar in the first direction by the first driving device while it is supported on one side by the first guide bar. The second stage is driven along the second guide bar in the first direction by the second driving device while it is supported on one side by the second guide bar. In this case, the first guide bar and the second guide bar can be placed close to each other by, for example, adopting a structure in which the other end of the first stage opposite from the side supported by the first guide bar is placed above the second guide bar, that is, in which a part of the moving range of the first stage is set above the second guide bar. This makes it possible to independently and freely move two stages in a footprint slightly larger than that of a single-stage type stage device.
The stage device may further include a third driving device for driving at least one of the first guide bar and the second guide bar in the second direction. In this case, since the first guide bar and the second guide bar can be moved close to and apart from each other, any serious problem is not caused by the structure in which the other side of the first stage opposite from the side supported by the first guide bar is placed above the second guide bar and the other side of the second stage opposite from the side supported by the second guide bar is placed above the first guide bar, that is, in which the moving range of the first stage and the moving range of the second stage partly overlap with each other. Therefore, it is possible to independently and freely move the two stages in a footprint approximately equal to that of a single-stage type stage device. In particular, in a case in which the third driving device independently drives the first guide bar and the second guide bar in the second direction, the two stages can be independently and freely moved in two-dimensional directions. This further reduces the size of the stage device.
Preferably, the point of action of driving force in the first direction is set at the center of gravity of each of the first and second stages. This can prevent unnecessary rotation moment from acting on the first and second stages when the stages are driven in the first direction.
The stage device may further include: a first table disposed on the first stage so as to hold a first sample; a first minutely driving device connected to the first stage so as to minutely drive the first table in at least one degree-of-freedom; a second table disposed on the second stage so as to hold a second sample; and a second minutely driving device connected to the second stage so as to minutely drive the second table in at least one degree-of-freedom. In this case, when the first table is minutely driven in at least one degree-of-freedom by the first minutely driving device, the first stage is turned by a predetermined amount on a predetermined rotation axis passing through the center of gravity thereof by reaction force produced due to the minute driving of the first table, thereby absorbing the reaction force. Similarly, when the second table is minutely driven in at least one degree-of-freedom by the second minutely driving device, the second stage is turned by a predetermined amount on a predetermined rotation axis passing through the center of gravity thereof by reaction force produced due to the minute driving of the second table, thereby absorbing the reaction force.
The stage device may further include: a first restraint force generating mechanism for generating restraint force for restraining a change in attitude of the first stage resulting from reaction force produced due to the minute driving of the first table; and a second restraint force generating mechanism for generating restraint force for restraining a change in attitude of the second stage resulting from reaction force produced due to the minute driving of the second table. This makes it possible to restrain or prevent a change in attitude of the first table or the second table, as necessary.
The stage device may further include a control device for subjecting the first restraint force generating mechanism to feed-forward control in synchronization with the driving of the first table by the first minutely driving device and for subjecting the second restraint force generating mechanism to feed-forward control in synchronization with the driving of the second table by the second minutely driving device. In this case, it is possible to prevent changes in attitude of the stages. That is, it is possible to minutely drive the first table and the second table while maintaining the original positions of the first stage and the second stage.
According to a second aspect of the present invention, there is provided an exposure apparatus for forming a predetermined pattern on a substrate by exposing the substrate to an energy beam, the exposure apparatus including the stage device in which the substrate is mounted on the first table and the second table as the first sample and the second sample.
Since the exposure apparatus includes the stage device, the footprint of the stage device can be limited so as to be slightly larger than that of a single-stage type stage device. Furthermore, at least one of substrate replacement and alignment can be effected on one of the tables concurrently with exposure of a substrate on the other table. Furthermore, reaction force against the force of driving of the first table by the first minutely driving device will not vibrate the second table, and reaction force against the force of driving of the second table by the second minutely driving device will not vibrate the first table. For this reason, for example, even when one of the tables is driven to subject a substrate thereon to alignment, reaction force produced due to the driving will not vibrate the other table where exposure is effected. Therefore, it is possible not only to reduce the footprint, but also to enhance throughput by concurrently processing the substrates on the two tables and to enhance exposure accuracy.
The exposure apparatus may further include a first restraint force generating mechanism for generating restraint force for restraining a change in attitude of the first stage resulting from reaction force produced due to the minute driving of the first table, and a second restraint force generating mechanism for generating restraint force for restraining a change in attitude of the second stage resulting from reaction force produced due to the minute driving of the second table. In this case, for example, high-precision focusing and leveling control can be exerted on the table on the stage where exposure is effected (that is, a substrate on the table) by restraining a change in attitude of the stage by the corresponding restraint force generating mechanism.
The exposure apparatus may further include a control device for subjecting the first restraint force generating mechanism to feed-forward control in synchronization with the driving of the first table by the first minutely driving device and for subjecting the second restraint force generating mechanism to feed-forward control in synchronization with the driving of the second table by the second minutely driving device.
The exposure apparatus may further include: a single mark detection system for detecting a position detection mark formed on the substrate on each of the first and second stages when the stage is moved into a first region; and a single projection optical system for projecting the energy beam onto the substrate on each of the first and second stages when the stage is moved into a second region.
A second embodiment of the present invention is to provide an exposure apparatus having a shortened overhang cantilever. The footprint of the shortened overhang cantilever is compact and is synchronized to compensate for the reduced overhang. The exposure apparatus may further include X and Y trim adjustment motors for making minor adjustments.
According to the stage device of the second embodiment, a distance between the first guide bar and the second guide bar is defined as a predetermined minimum such that the first stage and the second stage move in a synchronized manner. The first stage and the second stage are formed in the shape of a cantilever. The overhang distance of the cantilever is minimized such that the cantilever is long enough to be placed adjacent to a wafer loader located on a side of the stage device.
In the above stage device, a first table disposed on the first stage holds a first sample and a second table disposed on the second stage to hold a second sample. The overhang distance of the cantilever is minimized such that the first sample on the first table and the second sample on the second table are exposed and aligned, respectively. The movement of the exposure and alignment of the samples is synchronized into similar predetermined regions on the samples. At least two predetermined regions are defined above and below a centerline through the first and second sample. The predetermined regions being simultaneously exposed and aligned are defined above the centerline. In a second region, the predetermined regions being simultaneously exposed and aligned are defined below the centerline. And, in a third region, the predetermined regions being simultaneously exposed and aligned are defined at approximately near the centerline of both samples.
A third embodiment of the present invention is to provide an exposure apparatus having a reaction frame configuration including X and Y magnets, and X and Y coils. A pair of Y-axis linear motors (or third driving devices) include a Y magnet and a Y coil, respectively. The Y magnet is constructed in the shape of a sleeve having a rectangular shaped cross section. At least a portion of the rectangular sleeve (or Y magnet) is attached to the first guide bar. The Y coil is bordered by the two frame guides and extends longitudinally (in the Y direction) between two reaction frame supports. The rectangular sleeve shaped Y magnet encircles the Y-coil and frame guides and translates in the Y direction. The Y magnet and the Y coil are opposed thereto and constitute a moving coil type Y-axis linear motor.
A fourth embodiment of the present invention is to provide an exposure apparatus having shortened first and second guide arms.
According to the stage device of the fourth embodiment, the third driving force drives the at least one guide bar at one end. The first stage extends and retracts in a direction parallel to the longitudinal axis of the first guide bar; and the second stage extends and retracts in a direction parallel to the longitudinal axis of the second guide bar. Further included in the stage device of the fourth embodiment is at least one guide bar having an anti-torque actuator located at the one end for counteracting the torque being applied by translating forces acting on the guide arms and the wafer stage tables.
In another aspect of the present invention, a method and apparatus is provided for switching stage configuration sequences. Since rapid exposure of wafers is desirable in an exposure apparatus, the faster that a wafer positioned under an exposure lens can be replaced with a wafer from under the alignment lens, the greater the efficiency and throughput manufacturing of exposed wafers.
Further objects, features, and advantages of the present invention will become apparent from the following description of the preferred embodiment with reference to the attached drawings.